The field of the invention concerns devices for taking samples of body fluids such as blood, and in particular multiple sampling needles having one-way valve assemblies to prevent backflow.
One-way valves, such as those of elastomeric composition, are effective in preventing backflow, but it is often desirable to have the fluid collected at a higher rate. Elastomeric valves restrict fluid flow because of the restraint force caused by the elasticity which maintains such valves in a normally closed position.
In blood-sampling needle assemblies utilizing singular elastomeric valves, flow rate reductions (or fill time increases) can be 60% or higher as compared with the use of no valve at all. For this reason, medical personnel often prefer using the valveless assembly even though there is the risk of some backflow. Because the blood is commonly mixed with chemicals such as anticoagulants once it is withdrawn, there is the possibility of these chemicals entering the bloodstream.
Another problem associated with the use of blood-sampling devices having only one valve is that failure of the valve will result in no sample being withdrawn at all. This necessitates another injection of the patient, which is inconvenient for both the staff and the patient.